There's a lot of useless info in this question, which is there to confuse you.
They dated the fossil to 328-359 million years old. So find these values on the x-axis and see which order existed at that time. You can see that the only one that's still around during that period is order Q, hence C is the answer.
I did that, but when I looked at the x axis, the time period that 328-359 mya was in was 'Carboniferous.' There are no points in that area, and the closest point to that area is Z, which wasn't an option.
Am I missing something?
EDIT:
Oh, wait, I think I get it.. Does the entire line represent when the trilobites were distributed, and not just the letter at the end? If so, I understand how to do it!